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The process of pad printing is to etch the designed pattern on the printing plate first, apply the ink to the etching plate, and then transfer most of the ink through the silicone head to the object to be printed.
What are the types of ink
Common inks are often used. This type of ink and additives can print character patterns on plastics, metal glass, nylon canvas and other materials. Its characteristics are low cost, strong adhesion, ideal color. However, it is not suitable for PE/PP, baking ceramics, etc., and the corresponding diluent agent should be selected according to the pattern text, area size and the adaptability of the substrate. The standard type is generally used.
How to design a fixture
According to the shape of the substrate, a special fixture should be designed and manufactured to firmly clamp the substrate, ensuring the printing accuracy and repeatability during the printing process, as well as the convenience and safety of the handling operation. For a large number of prints, in order to improve efficiency, a conveyor belt structure can be designed.
Plastic head model
The plastic head should have good ink absorption and deinking properties, good resilience, fatigue resistance, and solvent resistance. The size, shape, and hardness of the plastic head shall be selected according to the supplier's chart or physical model, and then a model specification shall be determined according to the actual conditions and life.
The deformation of the contact between the plastic head and the substrate should be as small as possible, and its diameter should be approximately 3mm. If the plate has many thin lines, the rubber head should be relatively soft. The extrusion depth of the plastic head and the substrate shall not exceed 1/3 of the height of the plastic head, otherwise the plastic head may be easily damaged and the ink case may be blurred in shape. The newly purchased rubber head has a layer of release agent on its surface, and it should be wiped with a clean cloth, ethanol or plate cleaner before use.
Composition of an electric pad printer
The main components of the electric pad printer are: plastic head, oil pan, scraper group, stepless speed regulation device, switch (running/manual), fixture lifting table and so on. Because it does not need the traditional air pump gas source, and adopts the mechanical transmission system with 220V power supply and electronic continuously variable transmission, the equipment has good stability, controllable precision, low cost, small size, easy use, and reliable quality.
The quality evaluation indicators of the scraper mainly include hardness, thickness, elasticity, and straightness of the knife edge.
Generally use 0.25mm better flat steel strip for scraper. Its edge should be sharp, smooth and straight, and it can fit tightly with the steel plate. If the blade is not sharp or defective, it will cause the ink to stick to the edge of the picture or the ink mark of the blade. The severe plate will be scratched. When used, the scraper should be at a certain angle with the printing plate to prevent the squeegee from falling into the dents of the printing plate, causing excessive scraping and damage to the graphics. The length of the scraper should be greater than the width of the pattern text near the plate. The pressure of the squeegee should be under the premise of scraping the non-graphical ink on the plate, and the smaller the better.
First, the control of process conditions
Printing press operation
Should be familiar with the working status of the main institutions at each stage and the operations that can be selected in turn. After the pilot test is normal, only the printing surface, buttons, and indicator lights should be used in principle.
Printing plate installation
The plate is fixed in the middle of the ink plate, and then the fixture of the substrate is adjusted so that the rubber head is aligned with the center of the plate and the center of the substrate, and the printing plate installation is completed.
Plastic head adjustment, control speed
In the printing operation, the drop and lift of the plastic head determine the transfer rate of the ink to a certain extent and affect the graphic formation. Therefore, under the premise of plastic head, substrate, ink flow and other adjustments in place, an appropriate slowdown in speed will help improve the quality of printed products.
Add solvent to control ink flow
According to the printing capacity of one-time ink solvent, the ratio of ink and solvent is generally chosen to be 1:2 (winter, spring, autumn)—2:5 (summer). That is, use a slow release agent when it is too hot or dry; on the other hand, use a fast drying agent if it is too cold or dry. For a certain period of time, a certain amount of diluted ink is added in advance according to the amount of ink used in the substrate.
Wet temperature control
The essence is to try to make the solvent in the ink have a relatively stable volatilization rate. A simple way to control temperature and humidity is to print in an air-conditioned workshop.
Second, problems and suggestions
Graphic distortion
Mainly by the plastic head load, hardness, surface radius of curvature and text thickness, size, depth and transfer center between the two relative deviation caused. Choose several models of plastic head, or use the normal steel plate in the past, remove the source of the fault, and select the correct process.
Ink and pale
Mainly caused by ink selection and improper use, the ink should not be too thin or have thick paste added.
Imprinted edges
Check whether the scraper is sharp or notch, whether the ink is too thin, and whether the rubber head or the steel plate is worn or not.
Printing inks for printing equipment
Pad printing machine is a kind of printing equipment, mainly used for plastics, toys, glass, metal, ceramics, electronic, IC sealing and so on. Pad printing is an indirect, collapsible head printing technology and is currently a major method of printing and decorating the surface of various objects.